I'm sorry to tell you that if both cancers are advanced and have spread, to be honest, their survival time is about 2-5 months (especially after gastric cancer and bone cancer surgery). Gastric cancer and bone cancer are very painful in the late stage, especially bone cancer. Treatment is mainly to relieve the pain of patients, don't give up. Be sure to cooperate with the methods adopted by doctors and actively treat them! Now western medicine estimates that there is no good way. You might as well find an experienced Chinese medicine practitioner to treat it with Chinese medicine, or it may prolong life!
Even if you don't have surgery, it won't take long, because your mother is two kinds, and both of them spread in the late stage. A single one, active treatment can survive for 2 years!